1. Field of the Invention
The present invention relates in general to a reciprocating compressor used for compressing gaseous refrigerant, coming out of an evaporator, thereby increasing the pressure and temperature of the refrigerant prior to supplying the refrigerant to a condenser in cooling mechanisms such as refrigerators and air conditioners.
2. Description of the Prior Art
U.S. Pat. No. 4,759,693 discloses an example of typical reciprocating compressors which are used for compressing gas refrigerant, coming out of an evaporator, thereby increasing the pressure and temperature of the refrigerant prior to supplying the refrigerant to a condenser in refrigerators or air conditioners. In the above U.S. reciprocating compressor, the refrigerant inlet passage is constructed such that it directly contacts with the cylinder cover. In this regard, the gaseous refrigerant is heated by the cylinder cover to a high temperature while it is introduced into the compressor through the inlet passage. In addition, the gaseous refrigerant is brought into direct contact with the cylinder cover, thus generating operational noise. In order to overcome the above problems, the above compressor includes a plastic housing and a suction nipple. The above plastic housing has first and second shells, while the suction nipple is formed of plastic material, having a thermal resistance higher than that of the shells, through extrusion.
Several types of compressors, which are suitable to prevent a possible increase in refrigerant's specific volume and improve productivity and reduce the cost of the compressor, have been actively studied and proposed recently.
FIGS. 1 and 2 show the construction of a representative example of the studied and proposed compressors suitable to achieve the above objects. As shown in these drawings, the compressor includes a hermetic casing 1 which tightly seals the interior of the compressor. Placed in the upper section inside the casing 1 is a motor unit which generates a rotating force. The motor unit includes a stator 3, which is fixed inside the above casing 1 and forms a magnetic field when it is applied with external electric power. The above motor unit also includes a rotor 5 which is placed inside the stator 3 and rotates by the magnetic field of the stator 3. The above compressor also includes a power transmitting unit which includes a crank shaft 7. The crank shaft 7 is tightly fitted in the center of the rotor 5 and extends downward so the shaft 7 rotates in accordance with the rotating motion of the rotor 5. The lower end of the above crank shaft 7 is coupled to one end of a connecting rod 9 which extends laterally. The above connecting rod 9 converts the rotating motion of the crank shaft 7 into a reciprocating motion of a piston 11 when the crank shaft 7 rotates by the rotating motion of the rotor 5. The above compressor further includes a refrigerant compressing unit. In the above compressing unit, the piston 11 is coupled to the other end of the connecting rod 9 and is received in a cylinder block 13 in order to reciprocate in the cylinder block 13 by the reciprocating motion of the connecting rod 9. The above cylinder block 13 guides the reciprocating motion of the piston 11 and defines a refrigerant compressing chamber. A valve plate 15 is mounted to one side of the cylinder block 13 thus forming the compressing chamber in cooperation with the piston 11. The above valve plate 15 is provided with refrigerant suction and exhaust ports 15a and 15b. The above compressing unit also includes a cylinder head 17 which is tightly mounted to the valve plate 15. The above cylinder head 17 has suction and exhaust chambers 17a and 17b.
A gasket 19 is interposed in the junction between the cylinder head 17 and valve plate 15 in order to seal the suction and exhaust chambers 17a and 17b of the cylinder head 17. The above cylinder head 17 is formed through casting.
A pair of first fitting through holes 17c are formed on the cylinder head 17, while a second fitting through hole 17d is formed on the head 17 between the above first holes 17c as shown in FIG. 2. The first and second fitting holes 17c and 17d communicate with the suction chamber 17a of the cylinder head 17. A thin steel pipe or a refrigerant suction pipe 21 is fitted in each first fitting hole 17c, while a plug 25 is fitted in the second fitting hole 17d. The above plug 25 in turn is coupled to a capillary tube 23.
The other ends of the above first fitting holes 17c are connected to a suction muffler 27 thus allow the suction muffler 27 to communicate with the suction chamber 17a of the cylinder head 17. The lower end of the capillary tube 23 is immersed in oil contained in an oil chamber 29.
In the operation of the above reciprocating compressor, the stator 3 forms a magnetic field when it is applied with external electric power. The rotor 5 is thus rotated by the magnetic field of the stator 3, thereby causing the crank shaft 7 to rotate at the same time. The rotating motion of the crank shaft 7 is converted into a reciprocating motion of the connecting rod 9. In accordance with the above reciprocating motion of the connecting rod 9, the piston 11 performs a linear reciprocating motion inside the cylinder block 13.
When the piston 11 in the above state moves in the direction shown in an arrow A of FIG. 1, a suction force is generated in the cylinder block 13. Due to the suction force, the gaseous refrigerant is sucked into the suction chamber 17a of the cylinder head 17 through the suction muffler 27 and refrigerant suction pipes 21. The refrigerant in turn is introduced into the cylinder block 13 through the suction port 15a of the valve plate 15.
Meanwhile, when the piston 11 moves in the direction shown in an arrow B of FIG. 1, an exhaust force is generated in the cylinder block 13. The high temperature pressurized refrigerant in the cylinder block 13 is thus exhausted to the exhaust chamber 17b of the cylinder head 17 through the exhaust port 15b of the valve plate 15.
During the above operation of the compressor, the gaseous refrigerant flowing in the suction pipes 21 is heated to a high temperature by the stator 3 and rotor 5 of the motor unit. In addition, the refrigerant in the suction chamber 17a of the cylinder head 17 is heated by the compressing heat which is generated by the compressing motion performed inside the cylinder block 13. In addition, the heat of the high temperature pressurized refrigerant which is exhausted to the exhaust chamber 17b is transferred to the refrigerant in the suction chamber 17a through the valve plate 15 and cylinder head 17.
Therefore, the refrigerant in the suction chamber 17a is saturated and becomes a high temperature saturated refrigerant. The specific volume of the refrigerant is thus increased in order to reduce the amount of circulating refrigerant and to reduce the compressing efficiency of the compressor. Due to the above reduced compressing efficiency, the refrigerating and energy efficiencies of the compressor are reduced.
In order to produce the above compressor, several soldering processes are required to fix the plug 25 fitted in the second fitting hole 17d of the cylinder head 17, the capillary tube 23 coupled to the above plug 25 and the suction pipes 21 fitted in the first fitting holes 17c. In addition, the gasket 19 is interposed in the junction between the valve plate 15 and cylinder head 17. Therefore, the above compressor increases the cost but reduces productivity.